Pelvis and Lower Extremity

Question 1

Parts of the Hip Bone

Answer 1

sacrum

ilium

pubis

ischium

Question 2

Parts of the the Ilium

Answer 2

• ala (wing)
  
  • iliac crest
  • iliac tubercle
  • anterior superior and inferior iliac spine
  • posterior superior and inferior iliac spine
  • greater sciatic notch
  • iliac fossa
  • auricular surface
• body
• arcuate line

Question 3

Parts of the Ischium

Answer 3

• body
  
  • ischial spine
  • ischial tuberosity
  • lesser sciatic notch
• ramus

Question 4

Pubis

Answer 4

• body
  
  • symphyseal surface
• superior pubic ramus
  
  • pecten pubis
  • pubic tubercle
  • pubic crest
• inferior pubic ramus
  
  • +ramus of ischium –> ischiopubic ramus

Question 5

Acetabulum

Answer 5

• ilium + ischium + pubis
• hip joint socket

Question 6

Pubic arch

Answer 6

• formed by left and right ischiopubic rami
• inferior border is subpubic angle

Question 7

Parts of the Sacrum

Answer 7

• fusion of 5 sacral vertebrae
• ala
  
  • auricular surface
• sacral promontory - S1
• superior articular processes - S1
• ventral and dorsal sacral foramina
• sacral canal
• sacral hiatus - 30th and 31st spinal nerves
• auricular surface

Question 8

Coccyx

Answer 8

• fusion of 4 rudimentary coccygeal vertebrae

Question 9

Pelvic Foramina

Answer 9

• sciatic foramnia - notches + sacrospinous ligament + sacrotuberous ligament
  
  • greater sciatic foramen - leads to gluteal region
  • lesser sciatic foramen - travel from gluteal to perineum
• obturator foramen - leads to medial thigh
• sacral foramina
• sacral hiatus

Question 10

Sacrospinous Ligament

Answer 10

• from sacrum to ischial spine
• deep to sacrotuberous ligament
• prevents rotaiton of sacrum
• helps for sciatic foramina

Question 11

Sacrotuberous Ligament

Answer 11

• sacrum to ischial tuberosity
• prevents rotation of sacrum
• helps form sciatic foramina

Question 12

Pelvic Brim

Answer 12

• pubic symphysis
• pubic crest
• pecten pubis
• arcuate line of ilium
• anterior border of the ala of the sacrum
• sacral promontory

Question 13

Superior Pelvic Aperture

Answer 13

• bounded by the pelvic brim
• separates greater/false/major pelvis from lesser/true/minor pelvis
• Ob/Gyn correlate:
  
  • anteroposterior diameter is narrowest fixed distance through which baby’s head must pass

Question 14

Greater Pelvis

Answer 14

• also false or major pelvis
• technically part of abdominal cavity
• between the iliac fossa
• superior to pelvic brim

Question 15

Lesser Pelvis

Answer 15

• also true and minor pelvis
• forms pelvic cavity
• below pelvic brim

Question 16

Inferior Pelvic Aperture

Answer 16

• pubic symphysis
• ischiopubic ramus
• ischial tuberosity
• sacrotuberous ligament
• coccyx/sacrum
• Ob/Gyn correlate: interspinous distance is the narrowest non fixed distance through which baby/s head must pass

Question 17

Gynecoid Pelvis

Answer 17

• adapted for childbearing
• larger pelvic inlet - round/oval, broader sacrum
• larger pelvic outlet - wider pubic arch, greater subpubic angle (~90), greater interspinous distance

Question 18

Android Pelvis

Answer 18

• heart-shaped pelvic inlet
• heavier
• more prominent protuberances
• aucte subpubic angle (50-60 degrees)

Question 19

Perineum

Answer 19

• 3D diamond-shaped region between the thighs
• inferior to pelvic diaphragm
• urogenital triangle - anterior half of perineum
  
  • urethra, vagina, base of penis
• anal triangle - posterior half of perineum
  
  • ischioanal fossae, anal canal

Question 20

Joints

Answer 20

• sacroiliac
• pubic symphysis
• lumbosacral
• sacroccygeal

Question 21

Sacroiliac Joints

Answer 21

• multiple synovial joints between articular surfaces of sacrum and ilium
• weight-bearing joints with little mobility
• ligaments
  
  • anterior and posterior sacroiliac ligaments
  • sacrotuberous ligament
  • sacrospinous ligament

Question 22

Pubic Symphysis

Answer 22

• secondary fibrocartilaginous joint between symphyseal surfaces of pubic bones
• strong joint - some mobility, esp during childbirth
• ligaments:
  
  • superior and inferior pubic ligament

Question 23

Lumbosacral Joint

Answer 23

• secondary cartilagenous joint between L5 and S1 - intervertebral disc
• ligaments
  
  • anterior and posterior longitudinal
  • iliolumbar - prevents rotation of L5 vertebra on sacrum

Question 24

Sacrococcygeal Joint

Answer 24

• secondary cartilaginous joint between S5 and coccygeal vertebrae
• flexion and extension

Question 25

Ligaments

Answer 25

• iliolumbar ligament
• anterior and posterior sacroiliac ligament
• sacrospinous ligament
• sacrotuberous ligament
• superior and inferior public ligament

Question 26

Piriformis

Answer 26

• O: anterior sacrum and ischium
  
  • along posterior wall
  • exit via greater sciatic foramen
• I: greater trochanter of femur
• A: lateral rotation of thigh
• N: nerve to the piriformis

Question 27

Obturator Internus

Answer 27

• O: medial surface of obturator foramen
  
  • covers lateral wall
  • exits lesser sciatic foramen
• I: greater trochanter of femur
• A: lateral rotation of thigh
• N: nerve to obturator internus
• covered by obturator fascia

Question 28

Obturator Fascia

Answer 28

• pelvic fascia that covers obturator internus muscle
• tendinous arch - thickening of obturator fascia within pelvic cavity
  
  • body of pubis to ischial spine

Question 29

Pudendal Canal

Answer 29

• tunnel formed by obturator fascia within ischioanal fossa
• transmits pudendal neurovascular bundle

Question 30

Pelvic Diaphragm

Answer 30

• muscular floor of the pelvis
• separates the pelvic cavity from the perineum
• 2 parts:
  
  • levator ani
  • coccygeus

Question 31

Coccygeus

Answer 31

• O: ischial spine
• I: lateral aspect of sacrum and coccyx
• A: support
• I: S3-5

Question 32

Levator Ani

Answer 32

• parts:
  
  • pubococcygeus
  • puborectalis - voluntary resistance to defecation
  • iliococcygeus
• support of pelvic viscera - resist downward pressure
• uorgenital hiatus - urethra, vacina, deep dorsal vein
• anal hiatus - anorectal junction

Question 33

Nerves of the pelvis

Answer 33

lumbosacral trunk (L4-5)

sacral plexus

nerve to the obturator

pudendal nerve

Question 34

Obturator Nerve

Answer 34

• branch of lumbar plexus
• exits through obturator canal
• supplies muscles and skin of medial thigh

Question 35

Sacral Plexus

Answer 35

• lumbosacral trunk + ventral rami of S1-4
• branches:
  
  • superior gluteal nerve
  • inferior gluteal nerve
  • nerve to piriformis
  • nerve to obturator internus
  • nerve to quadratus femoris
  • posterior femoral cutaneous nerve
  • sciatic nerve

Question 36

Pudendal Nerve

Answer 36

• sacral plexus, S2-4) –> greater sciatic foramen –> gluteal region –> lesser sciatic formane –> pudendal canal –> perineum
• terminal branches:
  
  • inferior rectal nerve - external anal sphincter, levator ani
  • perineal branches - skin, perineal muscles, levator ani
  • dorsal nerve - penis/clitoris

Question 37

Coccygeal plexus

Answer 37

coccygeal nerve + S5

innervates skin of coccyx